Change of Tyre sizes, for the handling Experts

[bus_ter]

My Smart Roadster (RWD) is fitted with:

16" wheels,
Front: 6.5" wide
Back : 7" wide

All wheels are fitted from the factory with 205/45/R16 tyres.

These tyres look a little fat squashed on the front wheels and I have been considering the following change of tyre sizes to improve the look and handling.

Front: 195/45/R16
Back : 215/40/R16

My thoughts are these would be a better fit and improve the cars handling and looks. It also seems to be a more standard tyre setup for RWD cars.

Would this be a good idea?, or a bad idea and I should stick with the factory original size?

Any advice welcomed.

[Sam_68]

The change you are suggesting would make the car understeer quite a lot more, all other things being equal.

It's a safe condition at least, I guess, though most enthusiastic drivers would not see increased understeer as an improvement in handling.

There are ways to 'tune out' the adverse effect by playing with roll stiffnesses, in particular, but it would take an expert to sort it out for you and would require different springs or anti-roll bars fitting as well as the tyres, so not an easy solution.

You need to remember that Mercedes/Smart will have spent quite a lot of time testing and developing their car and will have tailored the suspension settings to give the best handling compromise with the tyres you have already... unless you value aesthetics more than handling, I'd leave well alone, if I were you.